Question 84General Subjects - Assistant Engineer

The correct answer is C) a ball bearing. A ball bearing is a type of rolling-element bearing that substitutes fluid friction for rolling contact friction. In a ball bearing, the rolling elements are spherical balls that rotate between two rings, reducing friction and allowing for smooth, efficient rotation. This is in contrast to sleeve bearings, plain bearings, and journal bearings, which rely on fluid film lubrication to reduce sliding friction rather than rolling friction. The other options are incorrect because they do not involve rolling-element bearings. Sleeve bearings, plain bearings, and journal bearings all use sliding contact rather than rolling contact to support the load, and thus do not substitute fluid friction for rolling friction.